The present invention relates to a load cell that transmits and measures linear forces along and moments about up to three orthogonal axes. More particularly, a compact load cell body is disclosed for minimizing heat affects on sensors present on the load cell body.
Transducers or load cells for determining forces along and moments about three orthogonal axes are known. Two such load cells are disclosed in U.S. Pat. Nos. 4,640,138 and 4,821,582. U.S. Pat. No. 4,640,138 illustrates a multiple axis load-sensitive transducer having inner and outer members that are joined by a pair of axially spaced spiders. The spiders comprise arms that are integral with the inner member and are connected to the outer member by flexible straps that have longitudinal links with the ends of the straps fixed to the outer member. The arms of the spiders are fixed to the center of the associated strap. Loads are sensed as a function of bending on the spider arms.
U.S. Pat. No. 4,821,582 illustrates a load transducer that measures linear forces in three axes and moments about two of the axes. The transducer has inner and outer structures connected by load sensitive spider arms or shear beams. The outer ends of the spiders are connected to outer links which are stiff when the inner structure is loaded in a direction along an axis perpendicular to the plane of the spider.
Each of the foregoing load cells can be affected adversely be heat. For instance, the load cell of U.S. Pat. No. 4,821,582 includes bearings allowing a shaft to rotate therein. The bearings are supported by the spiders, and thus, are relatively close to the sensing elements disposed thereon. However, the bearings are a source of heat due to rotation of the shaft. The load cell body, being constructed of thermally conductive material, can transfer heat to the sensing devices, which can affect the accuracy and/or life span of the load cell.
There is an ongoing need to provide an improved compact load cell that can measure components of forces and moments in plural directions and yet be easy to manufacture. Preferably, a load cell body of the load cell should also minimize heat conducted to the sensing devices.